High speed forging press



Feb. 29, 1944. N T 2,343,139

HIGH SPEED FORGING PRESS Original Filed Jan l5, 1940 4Sheets-Sheet 1 III7 INVENTOR WALTER ERNST ATTORNEYS Feb. 29, 1944. w; ERNST 2,343,139

I HI GH SPEED FORGING PRESS Original File d Jan; v15, 1940 4Sheets-Sheet 2 jBT'E.

[NVENTOQ WALTER ERNST- ATfbRNEYa Feb. 29, 1944. w, ERNST 2,343,139

I HIGH SPEED FORGING PRESS Original Filed Jan. 15, 1940 4 Sheets-SheetfiWORK Rcsn-rmu: I07

INVENTOR WALRR Emm RTTORNEYb Feb. 29, 1944. w, ERNST v 2,343,139 HIGHSPEED FORGING PRESS.

Original Filed Jan. 15, 1940 4 Sheets-Sheet 4 JTEr. 4.

, INVENTOR WALTER 'ERNST Anemia:

Patented Feb. 29, 1944 HIGH SPEED FORGING PRESS Walter Ernst, MountGilead, Ohio, assignor to The Hydraulic Development Corp., Ina,Wilmington, Rel a corporation oi Delaware Original application January15, 1940, Serial No.

1941, Serial No. 402,119

6 Claims.

The primary object of the present invention is to provide a means andmethod for operating a press where a relatively long working stroke ofthe press is necessary at relatively high speeds in order to economizetime in the cycle of operations and where the final stroke of the pressmust be at speeds as high as the initial speed and at high pressures.

It is an object of this invention to provide a press, for such purposesas forging of steels, injection molding, die casting and the like.Heretofore where a relatively long working stroke at high pressures hasbeen necessary, particularly in connection with forging presses, it hasnecessitated the use of a very large operating system of hydraulicaccumulators, the first cost of which was prohibitive. Also, due to therelatively short portion the working cycle is of the total cycle ofoperations the system was highly inemcient.

The object of this invention is to provide a movement to the work at lowpressure and high speed, giving a rapid traverse stroke; and tothereafter provide continued high speed at high pressure in order toimpart tremendous pressures to the work, preferably without suddenshock, as is required-in the case of forging metal billets, compressingplastics, etc.

Another'object of this invention is to secure the advantages of a closedcircuit with a reversible pump so that the direction of movement can bereversed without shock while securing the advantages of sudden highpressure. Thus shock is eliminated at the end of the reverse of thestroke which is. characteristic of the accumulator type of press.

It is a further object to protect the press and the entire systemagainst thelaccide'ntal de-' velopment of undue pressures, by theprovision of safety valves at the necessary points in the system.

The press of this invention is especially intended for operations inwhich it is desirable or Divided and this application July 1 die memberto press the heated billet downwardly, forcing it to assume the shape ofthe lower portion of the cavity. The length of stroke necessary toaccomplish this operation might be from several inches to more than afoot, depend ing on the particular workpiece in process. At any rate,the stroke must be executed rapidly, to prevent too great cooling of thepart, in. view of furthef pressing strokes yet to be performed.

' The first male die member must then be withdrawn, again at a high rateof speed, and a second die member moved into place. This done, anotherstroke of the press is efiected, either by manual or automatic controlmeans, for example to form the interior of the shell by displacing someof the previously formed metal upward- 1y into the space between the twodie halves. This operation, although requiring high pressures actingthrough a long stroke, must as before, be performed with great rapidity,to prevent the. cooling of the shell to the point of shrinking upon thepunch. Similarly, any subsequent pressing strokes will require rapidpress action, the more numerous and the deeper these are, the moreimperative becoming the high speed.

It is to meet the requirements of such a pressing operation, and to dothis with economy of equipment and space, and with smoothness andefllciency, that this press has been invented.

This case is a division of my prior application Serial No. 313,852 filedJanuary 15, 1940, an

entitled High speed forging press.

Referring to the drawings:

'Figures 1 to 4 are diagrammatic views of the press and its operatingsystem, showing the sig nificant stages of a pressing operation.

Figure 1 illustrates the idling stage of the press -and system,preparatory to a working stroke.

imperative to executea relativelylong high pressure stroke at'hi'ghspeed. Examples of such operations are found abundantly in forging,injection molding, or die casting. A specific example taken from thefield of power forging, .is the making of long steel shells. In thiscase a billet, heated to the correct temperature, is placed in thecavity of the lower die member, the

first of two or more pressing movements being immediately thereafterinitiated. This first movement might, for example, bring the upper maledie member into the cavity of the lower Figure 2 illustrates the'inltialstage of a working stroke, in which the press platen is caused to 1approach the work at a rapid -rate,'and under no pressure.

Figure} illustrates the reversing stage, the platen having completed itswork, and the press controls being operative to initiate its return.

Figure 4 illustrates the stage in which the platen is returning to itsidling position, and the auxiliary pressure system is storing workingenergy for the subsequent pressing cycle.

Referring in detail to Figures 1 to 4 of the drawings, the numeral Idesignates the pressing plunger of a hydraulic press, having at itsupper end the double-acting piston 2. Thispiston r'eciprocates withinthe cylinder -3.- At the lower end of the plunger I is mounted a platen4 upon which, in turn, is mounted the upper member.

of any suitable work-engaging means. such as a die or iniection. lunger.Disposed above the cylinder 2 and mounted thereon is a reservoir Iadapted to store part of the fluid medium by which the pressis operated.Y,

The movement of the platen 4, and the pressures exerted by it upon thework, are determined by two independent pressure generating systems, andby a third interconnecting hydraulic control system.- .There are thusthree distinct, but interrelated, hydraulic systems provided forthecontrol of the press: a primary pressure system, a secondary orauxiliary pressure system,

and an interconnecting control system. For the purpose of makingclear-the separate action of these systems, they will first be describedunder separate headings.

. mm Panssuns Svs'rrn The primary pressuresystem is of the closed typeand is operative throughout the entirety of a pressing cycle. It derivesits flow of pressure fluid from the pump 2, which is of the reversible,variable delivery type, capable of generating high ring .of this pumpconsist of a pilot cylinder I and a self-centering spring cylinder 2,the design of which is well known, and does not constitute a part of thepresent invention. u

' The pump l-delivers fluid to the differential areas of the presspiston 2 in accordance withdeliver into line H, withdrawing'from lines2'- and I0, and .thus effect the reverse or upward stroke of the piston.depen g upon the setting of the shift ring to the ght or left of thecenterof the pump.-

When a downward. pressing stroke piston 2 late be eflected, the solenoidI2 is energized (by means to be hereinafter described), its resultantmotion (see Figure 2)'being' transmitted to the shift ring of pump 2through the servomotor as described above, the pump then supplying fluidto line 9, and withdrawing it from line H. When the-pressing stroke thusinitiated hasbeen completed, the solenoid is de-energized (see Figure 3)and the pump is shifted to reverse it delivery by means of a springwithin the servom0tor,- thus to efl'ect an upward, return motion of thepiston 2. As this piston nears thelimit of its upward travel, thecontrolrod I 2, which is carried by platen 4, acts through an adjustablecollar 22 to move lever l4 and ultimately the pump shift ring to theirneutral positions, in which both pump 8 and piston 2 are caused to idle.Should any leakage of fluid occur to permit piston 2,

. pressures. Preferably the controls for the shift with plunger l andplaten 4, to descend of their own weight, control rod l2 and collar 22will correspondingly descend, permitting the ,pump to again deliver tothe push-back side of piston 2, restoring it to its idling position.This condition of the press is shown in Figure l.

In addition to the press controls thus far described, there are providedcertain other conand the fluid in the reservoir at certain stages of apressing cycle. For example, when piston 2 and platen 4 move downwardlyat the beginning of a pressing cycle, they do sounder theinfluence ofgravity, and at a rate determined by the suc- The position of the shiftring is primarily determined by the action of the operating solenoid l2and the platen-actuated control rod l2, which transmit their respectivemotions through the lever l4 and linkage is to the pilot plunger ii. Thereciprocation of thisFpilot plunger is .in turn transmitted to the shiftringof the piunp through the hydraulically actuated piston withincylinder 1, this piston being adapted to move directly, in direction andextent, with the pilot plunger.

'I'hesource of fluid pressure for thisise'rvomotor action is theconstant deliverypilot pump l1, which draws fluid from the reservoir Ithrough linesfli2 and l2,-dischar8ing it through'line' 22 f to oneofthe'ports of arelief valve 2|. Since the requirement ofthe servomotorfor operating fluid is intermittent, as determined by solenoid andcontrol rod-1'12, ,this relief valve normally bypasses the dischargeofpilot pump l1 into'line "22-. and back to the suction side of the pumpthrough line is. When, however, the control element-s12 and I2 set tocause movement of the pilot plunger It in either direction, fluid.pressure within the servomotor is momentarily loweredyand'the springwithin the relief valve 2| 'nioves the valve plunger to close thepassage between lines 20 and 22. This result in directing tion of thepump 6 drawing fluid from the lower end of press cylinder 2. As the areain this end of the cylinder is relatively small, being only as large incross section as the push-back side of piston 2, the piston tends totravel downwardly at a speed considerably greater than that at which thepump 8 delivers fluid through lines 2 and III to the upper, pressingside of the Piston 2.

' 2I downwardly against the spring 22, opening a the-output of thepilotpump into the servomotor through line 22, eifecting the requiredmovementof the pmnp shift ring. The exhaust of fluid from the servomotoris by way of lines 24 and 22, either to pump I! or reservoir 5.

passage'between the fluid in reservoir 5 and the space-above piston 2 byway of ports 22 and 22. The space above the piston is thus fllled asrapidly as the pump 8 can remove fluid from the lower end of cylinder 2,making the advance of the platen towards the work as rapid as possible.

As soon as the platen 4, or the workmember carried by it, contacts thework, pressure is developed in the upper end of cylinder 2 above piston2, closing the surge valve 22 by moving piston 2 is'driven upwardly byfluid pressure bearme against its push-back area, this pressure iscommunicated by the lines 2|, 22 and 22 to the head of a plunger 24 inthe upper part 01' the surge valve 20. The plunger is moved downwardlyagainst the compression of spring 2|, its

lower extremity striking the upper surface of the valv member 21,forcing it open against spring 22. This opening of the surge valve againassists in a rapid motion of piston ,2, in this instance by providing afree passage into the reservoir for fluid above the piston in excess ofthat 52 stands in the branch line 32, protecting therequired by pump 6to fill the push-back area of cylinder-3.

At the moment of reversal of platen 4, two other control valves areoperative. One of these, the tonnage control valve, is designatedgenerally 36. This valve, in fact, initiates the reversal of the platenby causing the de-energization of the solenoid I2 upon the attainment ofthe desired pressureupon the work. This pressure is communicated to thevalve through lines 37 and 39, which are branches of the main pressgreline lllleading to the area above piston 2. From line 38 the pressure isdirected against the end of the plunger 39, lifting it in opposition tothe force exerted by a compression spring 40. This movement of plunger39 is transmitted to a cam 4| carried at its upper end, the cam beingadapted to trip a normally closed limit switch 42, in series with thecontactor circuit for the solenoid l2. The valve 36 is maintained inthis position as long as pressure .in line 38 exceeds the compression ofspring 40, the flow of fluid'through the valve being exhausted by theline 43 to the reservoir 5.-

It is to be understood that the tonnage control valve just described maybe replaced, for the purpose of reversing the motion of the platen.

by a limit switch responsive to the position of the platen. The othervalve which becomes operative at the time of press reversal is locatedwithin the reservoir 5, and is generally indicated at 44. Its purpose isto relieve the intense working pressure existing in the space abovepiston 2. and, while doing this, to by-pass to the reservoir thedelivery of pump 6 into line H toward the push-back area of piston 2.This pressure-relieving and pump by-passing action provides a shocklessreversal of the press. The valve 44 consists of the balanced plungers 45and 46. both of which are urged toward the right under spring pressure.Normally, the spring pressure upon plunger 45 positions this plunger soas to block the port 47 opening into the reservoir. as ,well as one endof an internal passage 48. Likewise, the spring pressure upon plunger 46normally positions it so as to block the port 49 opening into thereservoir.

During the working stage of the press. the

push-back side of the system, while valve 53 stands in the branch line31, protecting the working side of the system. Both safety valvesdischarge into the reservoir.

There is also provided a check valve 54, its purpose being to permitfluid stored within the reservoir to be drawn into the line 3| andthrough it andline H to the pump 6, this passag of fluid taking place atcertain times during the actual working stage of apressing operation.Its action will be more fully described later in connection with asummary of the combined actions of all three hydraulic systems of thisinvention.

As stated above. the primary pressure system is operative at all timesduring a cycle of the press. From the description of this system it willbe evident that this is the case; that the system is operativeimmediately upon the energization of the solenoid l2 to advance theplaten toward the work, that it is operative during the working stage todrive the platen downwardly at high pressure and that it is operative,upon de-energization of the solenoid l2, to return the platen to itsidling position and to maintain it in this position'until the initiationof a new cycle. The primary pressure system is, indeed, solely operativeto produce the first rapid work-approaching stroke of the press, and theentire return stroke. It is in the second, or working stage of the pressthat the primary pressure system is augmented by the auxiliary pressuresystem acting through the controls of the interconnecting system, andthese systems will now be considered.

AUXIILIARY PRESSURE SYSTEM -'I'he auxiliary pressure system has itspressure source in a pump 55. This is a variable delivery high pressurepump. and may be of any wellstroke, so that the pump will draw fluidfrom 31 and 50, overcoming the spring tension urging it to the right.When the working pressure reaches its predetermined limit and thetonnage control valve acts to reverse the delivery of pump 6. pressurewithin push-back line H is transmitted by lines 3| and 5| to the rightend of plunger 45, shifting it to the left against its spring, tension.Plungers' 45 and 46 being thus shifted, port 41, passage 48, and port 49are all uncovered. whereupon working pressurestanding in line 31 isrelieved through port 41 to the reservoir, and the delivery of pump 6 isby-passed through lines I 3| and 5|, passage 43, and port 49 to thereservoir.. Working pressure having been relieved. plunger 46 isspring-returned to its normal right-hand position, blocking port 49 andcausing the delivery of pump 6 to be directed against the pushback areaof piston 2. Aiso,'since this pressure above the piston 2 is relieved,push-back pressure the reservoir 58 through the line 59 and deliverpressure through line 60. The pressure cylinder 55 is connected by theline iii to a part of the pressure circuit in a manner later to bedescribed. so that when pressure is built up in this part of the circuitto a point determined by the tension of the spring in cylinder 51, thepressure will overcome the spring tension and return the shift ring ofthe pump. to neutral position, or nearly to neutral position. Underthese conditions, the pump will deliver just suflicient volume tomaintain pressure in the system asdetermined by the setting of thespring in cylinder 5'|.- Two hand wheels. 62 and 63. are provided, onefor adjusting the stroke of the pump. and one for adjusting the tensionof the spring. The design and operation of this control is well known bythose versed in the art.

A relief valve 64 is provided as a protection to preventexcessive'pressures being built u in line 60 or in other parts of theauxiliary pressure system. in the event the pump control should fallfrom any cause. This relief valve exhausts throu h line 65 to reservoir59. The shut-off 55 is delivered consists of a high pressure cylinder68, having a bore 6! in which is fltted piston II; and of an enlargedcylinder ll having a bore I! in which is fltted piston 13. The twopistons, II and II, are rigidly interconnected by the rod It. In thedrawings the cylinder ii is shown broken above piston 13, to indicatethat the height of this portion of the cylinder is dependent upon theparticular pressure drop to be allowed between the uppermost andlowermost positions of the piston. For instance, if a 20 per cent dropis decided upon, the total height of the cylinder will be flve times thestroke or the piston.

The space abov piston I3 is fllled with an elastic fluid medium; as forexample with air, or some inert gas-such as nitrogen, helium or pressurewithin the bore 9, it is subjected to that pressure through the valve'I'l only when the positions of pistons IO and 13 indicate that the pumphas fully performed its charging funcneon. It will be readily recognizedthat as fluid pressure is pumped into the bore i! of the accumulator 61,piston Ill, rod I4 and piston 13 will be pushed upwardly tocompress theelastic medium in bore 12 above piston 13.

Attached to piston Ill, asby rod I5, is a cam 16 which is locatedoutside the accumulator 61 and is adapted to actuatethe control valve'll, this valve being located in the line II and being designed tocontrol the stroke of pump ll. Valve 11 contains a piston "I8 on theright end of tion.- It will be noted that because of this provision,pump will always be delivering at its maximum rate during a downstrokeof piston ll, thus supplementing the stored volume of accumulator fluidin producing the high speed stroke of the press at high pressure.

For replenishing any of the gaseous medium that may be lost from theaccumulator, there is provided a supply line Ha, in which is placed ashut-oi! valve 'lib. Normally the valve lib is closed, the accumulatorrequiring no operating connection to its source of gas supply. When theaddition of gas to the accumulator is found necessary, valve Ilb isopened to permit a flow from the gas source to the accumulator. The

, pressure of the gas supply will be equal to the which is mounted aball, or roller, for contacting cam l8. Piston I8 is forced to itsextreme righthand position by a, spring 1:, this position of the pistonbeing seen in Figures 3 and 4. While in this position, the piston shutsoil passage of fluid from the line 80 to the line I, the line ll being abranch of line I leading to the fluid pressure bore 8! of theaccumulator 81. At the same time, line 6!, which is connected tothepressure cylinder 58, is in communication with lin 82, in turnconnected to exhaust line 83,

which leads to the reservoir 58. Under this condition, no pressure canexist in cylinder 56, and pump 55 will be held on iull stroke positionby.

the spring in cylinder 51, so that the full delivery of the pump isdirected into the accumulato 61, storing pressure fluid in the bore 9;

In Figure 4, the accumulator is shown nearly sued, with the piston n ofvalve "standing in its extreme right-hand position. A slight additionalupward movement or the accumulator piston, which position isillustratedin Figure 1. will bring cam 16 into contact with a roller onthe end of piston 18, forcing this piston to the left against thepressure of. spring 10. This action of the piston will close connectionbetween lines minimum gas pressure within the accumulator, that is,thepressure when piston I3 is at the bottom of its stroke.

The cylinder H is also provided, at its lower end, with a breather lineHe, the purpose oi. this line being to maintain atmospheric pressure onthe underside of piston 13'.

There. is provided in'thd upper end of cylinder 68 a port 84 by whichthedrain line 83 is connected to'the bore 69 above the piston head III.

This arrangement provides for conducting back to the reservoir 58 anyfluid which leaks past the piston head Ill from the lower, high pressureend oithe bore 69.

The reservoir ii is joined with the reservoir I of the primary pressuresystem by the pipe line II. Pressure fluid transferred from theaccumulator to the press is ultimately returned to the reservoir 58 fromwhich it originally was taken,

1 by being expelled into the reservoir I upon the lust sufllcient fluidinto the accumulator I! to maintain it fully charged.

The-provision of the valve I1 in the auxiliary pressure circuit insuresthat whenever the accumulator is not fully charged, the pump is willsupply pressure fluid to the accumulator 01 at its maximum outputcapacity. As indicated above, valve 11 is not actuated by cam l8, and'the control ll of the pump is not, therefore, sub.- iectcd 'to pressureswithin the accumulator 81, until cam Ilhasbeen carried by pistons II and13 almost to the upper limit of its travel, where the elastic mediumabove piston II has been retraction stroke of the press, and 11 8 intothe line I.

'Im'sncomcrmc Comor. Srsrsu The purpose-oi the systemnow to be describedthen overflowis .to release, during the working stage of they presscycle, the kinetic energy of the gaseous medium compressed above pistonit of the ac-,

accumulator.

The e of fluid from the accumulator is 1 through line II and valve 8'into line 81. The.

valve 88 is simply a service 'valve similar to the valve I, and isnormally fully open. Line '81 leads to a metering minim-pressure fluidbeing discharged from this valve through-a choke valve II and thence,through line as, to a pilot operated tw'o-way valve ll. A line .2leading from this two-way valve joins the main pressure lin ll,

-and it is by opening a passage into-this line at irom line II that thetwo-way valve ll opens a passage from the accumulator '1 to the press.

The open or closed position of valve ll is de-.terminedbypilotpressureinthelinesfl and It. This pilot pressure istakenfrom the pressure line ll through branch line ll, choke valve '0, andline I! tothe four-way pilot valve ll. Depending upon the setting oithis pilot valve, fluid is conducted from line I! into either pilotcompressed to the desired point, and the bore line I} or. forcontrolling the position of the two-way valve 9|. The setting of valve99 is determined by the energization or de-energization of a solenoid99, and by the compression of aby the pull of the solenoid core; When,however,

the solenoid 99 is de-energized, the spring I actuates the valve piston|0| so as to connect lines 91 and 93, exhausting line 94 to the drainline 93. a a

The solenoid is shown in its de-energized state in Figures 1, 2, 3 and4. From these views of the drawings and from the foregoing description,

it will be apparent that energization of the solehold 99 results in theopening of the two-way valve 9|, and that de-energization of thesolenoid results in the closing of this valve, by directing pressureinto pilot lines 94 and 93 respectively. The choke valve 99 standing inthe inlet line 91 of the pilot valve 99, regulates the fluid velocityinto the pilot lines 93 and 94, and consequently, the speed of openingor closing of the two-way valve 9|.

The purpose of the metering valve 99 and the choke valve 89 is toregulate the transfer of fluid from the accumulator to the press, oncethat flow has been started by the energization of solenoid 99 and theconsequent opening of valve 9|. The

setting of the choke valve 99 is responsible for the general rate atwhich the transfer of fluid takes place, while the metering valve 99, incooperation with the choke valve 89, serves to maintain that rateconstant against varying resistances ofiered by the work, and also, atthe moment of opening of valve 9|, serves to cushion the impact ofaccumulator pressure upon the press.

- Valves 99 and 99 may be regarded as two chokes in the pressure linebetween the accumulator and the press. Valve 99, after being manuallyad'- justed, is a fixed'choke, while valve 99 is a variable choke, itsrestriction of the pressure line increasingand decreasing inversely withpressures in line 90.

Briefly, the metering valve consistsof a plunger I02 urged in onedirection by a spring I03. The plunger I02 is provided with meteringflutes or grooves I04, these flutes permitting more or less passage offluid from the line 91 to the choke valve 89, as plunger I92 is raisedand lowered, respectively. The pressure on the inlet side of the chokevalve 99 is communicated to the end of the plunger I02 opposite thespring I93 by the line I05. The pressure on the outlet side of the chokevalve 99, that is, the pressure identical with that exerted upon presspiston 2, is communicated to the spring loaded end of the plunger I92 bythe line I09. 1

During the idling stage of the press, when no how ofpressure fluid istaking place through valves 98 and 99, pressures in the control linesI09 and I08 are identical and spring I03 holds the plunger I02 in itsuppermost position, where the flutes I04 present the least possiblerestriction to fluid now. This position of the metering valve is seen inFigure 1. At the instant that twoway valve 9| is opened to discharge theaccumulator, the pressure in line 90 on the outlet side of choke 99 willmomentarily drop, and this change will be communicated to the meteringvalve through line I08. The efiect of this sudden drop of pressurebearing upwardly against the plunger I02 will be to permit this plungerto move downwardly, pressure in line I05 still being, relatively high.Because of this downward motion, the restriction through the flutes I04is greatly increased, with the result that the tendency of accumulatorpressure fluid to rush into the pressing area of cylinder 3 is checked.Gradually, as pressure rises in line 90, the restriction at valve 99decreases and the rate of flow to the press increases. The meteringvalve thus releases accumulator pressure without shock upon the press.

During the pressing operation, varying work resistances will beregistered upon the metering valve plunger I02 through the line I09.

Lowered pressures in this line will permit the valve plunger tomovedownwardly under the influence of the pressure in line I95, thismovement resulting in a greater restriction of the fluid passage alongthe flutes I04, thereby reducing the flow from line 91 to the choke 99.Increased pressures, on the contrary, cause the valve plunger to moveupwardly, so that 'larger areas of the flutes'IM-are exposed to thefluid passage,

and the 'flow to valve 99 is increased. The press movement is thusmaintained at a constant rate, namely, the rate predetermined by themanual adjustment of choke 99.

Energization of the solenoid 99, to initiate the transfer of pressurefluid from the accumulator to the press, takes place just before theplaten 4 engages the work. To provide for this accurately timedenergization, there is attached to the platen a control rod IIlI havingthe cam face I99, this cam face being adapted to engage and close anormally open limit switch I99. The position of this limit switch isadjusted to meet the requirements of difierent pressing operations.

OPERATION or COMBINED SYSTEMS Idling in its idling, state, the platen 4being fully withdrawnfrom the work, and dwelling in this condition,although in readiness for a. pressing stroke. No appreciable flow ofpressure fluid is taking place in the primary system, the pump 9 beingheld in its neutral, no-delivery position by the upward force of thecollar 25 of the control rod I3 acting upon one end of the lever I4.Such flow as does occur is toward the push-back area of piston 2, and isdue 'to leakage of pressure fluid from this area, with the consequentlowering of the platen and actuation of the pump through collar 25, todelivery into line II an amount of fluid suflicient to compensate forthe leakage.

As to the auxiliary pressure system, the pump 59 has moved the pistonsI0 and I3 of accumulator 9! to their fully charged positions, and hasitself been shifted to neutral position in response to pressure withinbore 99. It is, at this time, operative only to restore the accumulatorto its maximum pressure state as fluid within the bore 99 is lostthrough leakage.

The accumulator is maintained in its -passive condition by the blockingof its pressure fluid in the interconnecting system, specifically at thevalve 9|, which is closed. This valve is forcibly maintained in itsclosed position by the action of static fluid "pressure from theaccumulator,

traoerse toward work When it is desired to start a pressingoperationcrease. In this event, pressure would be built up on-thepush-backside of the press. This presthe operator closes the energizingcircuit for the pump solenoid H. The pump 9 is immediately actuated todeliver at its maximum rate into lines Its entire fluid supply is takenfom the pushback side of this piston through line II. This piston, withplungeri and platen 4, drop of their own combined weights as rapidly aswithdrawal 9 and Illtoward the pressing side of piston 2,

of push-back fluid takes place. Since the-volume [into the pressingspace.

Figure 2 of the drawings illustrates'the condition just described,solenoid n being shown collapsed, arrows indicating the'direction offlow of fluid, the platen shown descending, and surge valve shownatically in its opened position. No change in the condition of theauxiliary and interconnecting systems has occurred,

.the solenoid 99 not yet having been energized.

Only the primary system is operative at this stage. 1

- Working stroke The distance from its idling' position to the workpiece having been traversed, the platen 4, through the rod I91 and camI98, actuates the limit switch I89, which controls the energizingcircuit for the solenoid 99, and closes this switch, thereby energizingthe solenoid. 99. By this ac- 7 tion, the platen of the press causes theinterconnecting control system to release the stored energy of theauxiliary pressuresystem, directing it to the pressing side of piston 2.Figure 3 of the Y drawings shows the press and the system controls inthe positions they assume immediately after.

this release of accumulated energy takes place. The flow of pressurefluid, is indicated by bold arrows, while the flow of pilot fluid isindicated by light arrows.

In the primary system, no significant change has occurred except thatthe surge valve has been closed bythe development of pressure in thespace above piston 2. The pump, however, continues to withdraw from thepush-back side of the piston 2, and to supply fluid, now underhigh'pressure, to the main working area of the piston.

Upon energization of solenoid 99, plunger l8| of pilot valve 98 is movedso as to expel the fluid from line 93 into line '83, while pilotpressure is conveyed into line 94 The two-way valve 8| is thus moved toits upper or open position and the flow oi. pressure fluid from line '99to lines 92 and I8 immediatelyensues. The rate at which this flow takesplace is governed by the Openin of the choke valve 89, and when thisvalve is appropriately adjusted by the operator, this rate will bsuch'a's to cause the pressing piston 2 to move into the work without areduction of its previous rapid traverse speed. -That is, the largevolume of pressure fluid supplied by the accumulator, added to thesmaller volume supplied by I pump 8 will equal the previous sum of themake- -:up volume from the reservoir 5 and the output of pump i.

It the operator has opened choke valve 99 too. much so that toogreat avolume of pressure gfluidis delivered from the accumulator into the 7press cylinder, the press speed may tend to inpressure 9|.

sure will act through line H and branch lines 31 and il into the valve44, which valve will thus be opened to relieve excess pressure fluid inthe press cylinder, just as at the time of press reversal. The action ofvalve 44 in this connection determines the maximum speed of pressing.

If the operator has opened valve 89 only partially, the working strokeof piston 2 will pro- -ceed at a rate slower'than thework-approachingrate, and some fluid will be drawn from the res-' ervoir5 through check valve 54 by the pump 8. The amount of fluid so drawnfrom the reservoir will be that required by pump 8 in excess Initiationof reversal The working stroke of the press continues at highppeed andhigh pressure until the pressure setting of the tonnage control valve 38is reached.

The actuation or this valve is the first event in x the initiation ofthe return of the press platen, its opening, and the actuation of othercontrols immediately thereafter ure 3.

In this figure the press platen has progressed downwardly to its limitfor the particular work piece in the press, as likewise the movingelement of the accumulator. Back pressure in line 38 to tonnage controlvalve 36 has collapsed the spring within this valve, moving cam 4| intoposition to open limit switch 42. As explained above, opening of thisswitch breaks the circuit to all electrical controls, and, consequently,solenoids l2 and 99 are now in their extended positions. I

Solenold l2, upon de-energization, has per-" mitted the spring withinthe control 'I of pump 8 to shift the pump to its full delivery positionin the direction of the push-back area of piston 2. This piston is, atthe moment, locked against movement by the extreme pressure on its uppersurface, and the discharge of pump 6 is conducted through branches 9iand SI to the by-pass and relief valve 44. The plunger 45 of this valveyields to the left under the pressure in line Si, and the output of pump8 is then by-passed through passage 48 and port 49 to the reservoir, theport." already being opened by the movement of plunger 46 to the leftunder the influence of working back-pressure in line 59. As soon as themovement of plunger 45 uncovers port 41, this back pressure is relieved,passage of fluid being from lines In to 31, and through port 41- to thereservoir. This action of valve -from the accumulator to the press, thisaction proceeding from the upward shifting of plunger I" of pilot valve98, and the reversal of pilot in the lines 83 and 94 to close the valvebeing illustrated by Fig- The pump 55 is, of course, delivering at itsfull rate into the line 60, having been put on stroke shortly after theengagement of the work by the press, and the opening of control line 6|through valve 11 to the reservoir by the downward motion of cam I6; Asthis cam has moved to a still lower position tha in Figure 3, the lineBI is still connected to the reservoir through valve Return strokeFigure 4 shows the return stroke of the press, I

and the simultaneous re-charging stroke of the accumulator. This view isrepresentative of the entire press return movement, no change in thesetting of the controls taking place until the idling position isreached.

The platen is returned solely by the delivery of pump 6 toward thepush-backside of piston 2. Part of the fluid above this piston is drawnupon by the pump through lines 9 and ill, the remainder being exhaustedthrough the surge valve 28 to the reservoir 5, from which the properproportion is carried by the pipe line 85 to the reservoir 58. The surgevalve is forcibly held open by the push-back pressure communicated *toit through branches 3| and 33 of line H. The action of the surge valvein this stage of the press cycle aids in producing a rapid motion of theplaten, just as in the work-approaching,

stage. In both stages, it serves to make up the diflerence in thevolumetric requirements of the cylinder 3 above and below the piston 2,the speed of the piston being determined by the full capacity of pump 6in delivering to, or drawing from the relatively small push-back area.

The valve ill of the interconnecting controls having closed at the pointof press reversal, it remains closed even though limit switch IDS iscontacted by cam )8 during the press return movement.

In the stage illustrated by Figure 4, the accumulator is being chargedat the full delivery rate of pump 55, the valve 11 preventing fluidpressure within bore 59 from being communicated to the pump control 56,until the cam 16 shifts the valve; indicating complete charging of theaccumulator.

Representative pressures The press as described lends itself to a widerange of pressures, of which -the following are to be considered merelyrepresentative.

Pressure upon the piston 2 may be at about 1250 pounds per square inchduring the working r pounds per square inch.

This is the pressure that would be exerted by the gaseous medium on thepressure fluid of the accumulator at the limit of the downward stroke ofthe accumulator pistons, or, in other words,

when the gas had reached its maximum allow- When the accumulator isfully charged and standing in its uppermost position, this pressurewill, of course, be higher. a typical increase being about 20 per cent.In the present able expansion.

working stroke of high press movement.

instance, this would give a maximum accumula-' P tor pressure or 1620pounds per square inch.

Again allowing for frictional losses in the accumulator and the circuit,the pump 55 would be designed for pressures greater than this maximum. Aloss of pounds or pressure, for ex- 'ample, would require that this pumphave a peak Summary of main features The press platen of this inventionis moved to andfrom the work at high speed by'the pump of a .primarypressure system, this pump also being operative to assist in effectingthe high pressure stroke.

There is provided an accumulator for adding pressure fluid to thatsupplied by the pump of the primary system, so as to produce a pressspeed-as well as high pressure. This accumulator is part of an auxiliarypressure system, having a separate pump and being charged by this pumpat full delivery in all except its fully charged position. The

pump stores hydraulic fluid in the accumulator,

and at the same time compresses a gas therein. At the appropriate timein a pressing cycle, the pressure. of this gas, reacting upon the bodyof hydraulic fluid, forces this fluid through an interconnecting systemto the press. 1

The release of accumulator pressure fluid is timed by the. position ofthe press platen acting through electrical control meansto open a valvein the interconnecting system. This occurs just prior to the closing ofthe press upon the work. The tendency of accumulator pressure to bereleased with shocking force upon the press is checked by a meteringvalve, responsive to pressures at the inlet and outlet of a choke valve,

' the latter being the manual control of the transations in thi rate.

positioned, the choke valve in the fluid transfer line makes possible apressing speed as high as the initial approaching speed of the press.This high speed is effective throughout as longa working stroke as thefluid storage capacity of the accumulator is designedto produce. 1 Anelectrical circuit is provided, in which originates the control impulsesfor starting-the press, releasing accumulator energy, and reversing theThe second of these steps is made dependent upon the first, so that itcan not occur during the return stroke.

Reversal of the press is accomplished either in response to the pressureor position attained by the press. Shock due to reversal is eliminatedby a valve which momentarily opens to relieve the high working pressureabove the press piston, and to by-pass thepump which at that moment hasbeen'actuatedto deliver toward the push-back side oi! the piston. 1 j

When properly An important advantage of the invention is of the pumpsproduces all other motions of the press. while the output of the otherpump simultaneously charges the accumulator.

It will be understood that I desire to comprehend within my inventionsuch modifications as come within the scope of the claims and vention.

Having thus fully described my invention, what the in- I claim as newand'desire to secure by Letters Pat nt is:

1. In combination in a hydraulic system, a pump: fluid operable meansfor moving said pump from full stroke to neutral position, anaccumulator adapted to be charged with fluid from said pump, valve meansnormally preventing fluid connection between said fluid operable meansand said accumulator, and means responsive to the connection betweensaidfluid operable means and said accumulator thereby causing said pumpto move to neutral position 2. The combination in a hydraulic system ofa pump. fluid operable means including a pressure chamber for movingsaidpump from full stroke to neutral position, an accumulator adapted-tobecharged with fluid from said pump, valve means including a valvemember normally preventing fluid-communication between said pressurechamber and said. accumulator, and means movably connected with saidaccumulator, and

'. adapted in response to a predetermined position of the latter toestablish said fluid communication to thereby cause said pump to move tosaid neutral position.

'3, The combination in a hydraulic system of a variable delivery-pump,fluid operable means operable to move said pump from full stroke tosubstantially neutral or no-delivery position, an accumulator adapted tobe charged with fluid from said pump, valve means interposed betweencompletion of the charging oi said accumulator for causing said valvemeans to establish fluid cause said pump to stop charging said accumulator.

4. In combination in a hydraulic system, a variable delivery pump, fluidoperable means operable to move said pump from full stroke tosubstafltially neutral or no-delivery' position, an

accumulator adapted to be charged with fluid from said pump, saidaccumulator including a cylinder with a fluid operable plungerreciprocably mounted therein, control valve means including a valvemember normally preventing fluid connection between said fluid operablemeans and 5 Q said cylinder, and means operable by-said plunger andadapted in response to a predetermined position of the latter to movesaid valve member into positionfor establishing said fluid connection,to thereby bring about a return of said pump to neutral position. l

5. In combination in a hydraulic system, a pump, means including apressure chamber for moving said pump-from full stroke to neutral, an

accumulator containing a piston which is actu-- ated by pressure fluidderived-from said pump. said fluid being admitted to said' accumulatoronly on one side of the piston, a flxed gas in said accumulator on theother side oi the piston, a control valve interposed between theaccumulator and the pump for controlling the flow of pressure fluid tothe accumulator, and means including a cam secured to said piston forclosing and opening said valve whereby when the valve is opened fluidpressure is admitted to one end I or said accumulator to compress thegas at the other end of the accumulator.

'6. In combination in a hydraulic system, a

fluid pressure pump, means including a pressure chamber for moving saidpump from full stroke to neutral, and -an accumulator of fluid energy,

said accumulator comprising a closed cylinder containing a double-headedpiston, the space betweenone side of said piston and the adjacent end ofsaid cylinder being in communication with the pump for the purpose ofactuating said piston, the space between the other side of said pistonand the adjacent end of said cylinder be ing filled with a compressiblegas so that as pressure fluid is admitted into the cylinder from saidpump said gas is compressed and the energy oi the compressed gas isavailable to force the pressure fluid at the opposite side or the pistoninto the hydraulic system, the end of the cylinder said fluid .operablemeans and said accumulator for controlling fluid communicationtherebetween, said valve means including a reciprocable member andyielding means normally holding said member'in position for preventingsaid fluid communication, and meanson said accumulator and adaptedinresponse to a predetermined position thereof to move said memberagainst the thrust of said yielding means into position for establishingsaid fluid communication, to thereby to which the pump is connectedbeing in communlcation with said pressure chamber or the pump through acontrol valve, said valve being controlled by the movement of the pistonin said accumulator during the compressing action of the compressiblegas to efl'ect a. return of the pump to neutral when the compressingoperation oi the gas hs been completed. and the is full of fluid energyderived from the pump.

' WALTER mms'r.

